An encoding control device of the prior art as shown in FIG. 1 includes a data input device 1 (usually a keyboard) and an encoding control unit 2 which has a data control device 21 and an encoding device 22. The encoding control unit 2 can be implemented in a single IC with an output pin (O/P), positive and negative power source pin V.sub.DD, V.sub.ss, and N data receiving pins pin1.about.PinN. The prior-art encoding control device works in the following way: in response to a press/release state of the keyboard 1, the control device 21 sends out numerical data to the encoding device 22 which accordingly executes a control action corresponding to the numerical data received.
Generally, an encoding control device has to receive a number of numerical data D1, . . . , DN to achieve diverse control effects, so the data control device 21 needs a corresponding number of pins (Pin1.about.PinN) for controlling data D1.about.DN which thus cannot cope with encoding control device of the current trend for minimizing the number of IC pins.